We propose to carry out active participation in the protocols of the NSABP in breast cancer research. We are currently entering patients into NSABP protocols B-06 and B-09. In addition, we are following 64 living patients from protocols B-04 and B-08. The protocols are designed to compare treatment modalities already available, i.e., radical versus total mastectomy (B-04); to test the efficacy of segmental mastectomy with or without radiation as compared with more conventional methods of treatment (B-06); to compare two drug versus three drug regimens of chemotherapy for patients with Stage II breast cancer (B-08); and to evaluate the anti-estrogen drug Tamoxifen combined with chemotherapy (B-09). All the protocols are designed to answer important questions about the biology and natural history of breast cancer via prospective, randomized clinical trials. It is our plan to continue to add patients to the active protocols (B-09 and B-06) and to continue with a very careful follow-up on those patients already entered into research protocols at this time.